leetcode:Merge Two Sorted Lists

1、

　　Merge two sorted (ascending) linked lists and return it as a new sorted list.

　　The new sorted list should be made by splicing together the nodes of the two lists and sorted in ascending order.

Given 1->3->8->11->15->null, 2->null , return 1->2->3->8->11->15->null.

 

2、思路

　　1、判断两数大小，小的话，插入

3、

　　

/**
 * Definition for ListNode.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int val) {
 *         this.val = val;
 *         this.next = null;
 *     }
 * }
 */ 
public class Solution {
    /**
     * @param ListNode l1 is the head of the linked list
     * @param ListNode l2 is the head of the linked list
     * @return: ListNode head of linked list
     */
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        ListNode dumary = new ListNode(0);
         //赋值
         ListNode lastNode = dumary;
         while(l1 != null && l2 != null){
             if(l1.val > l2.val){
                 lastNode.next = l2;
                 l2 = l2.next;
             }else{
                 lastNode.next = l1;
                 l1 = l1.next;
             }
             lastNode = lastNode.next;
         }
         if(l1 != null){
             lastNode.next = l1;
         }else{
             lastNode.next = l2;
         }
     return dumary.next;
    }
}